As discussed previously, other researchers have studied the decrease in hydrogen production that occurs during long-term APBR operation (Fontes Lima and Zaiat, 2012 and Penteado et al., 2013; and Fontes Lima et al., 2013). Based on the findings of these studies, it was used an estimated value of the Ritonavir concentration in the APBR to calculate the sOLR (Eqs. (1), (2), (3), (4), (5) and (6)).
To identify the optimal value of sOLR and obtain maximum values for VHP, a polynomial function was fit to the experimental data (Fig. 3) with the following result (Eq. (7)):equation(7)VHP=22450.76-72647.17(sOLR)+77290.12(sOLR)2-26253(sOLR)3R2=0.9722
Fig. 3. Correlation between volumetric hydrogen production mL-H2d-1Lreactor-1 and specific organic loading rate (g-Total carbohydrates g-VS−1 h−1) during APBR operation.Figure optionsDownload full-size imageDownload as PowerPoint slide
In this sense, it is strongly recommended that in future studies, the frequency and type of acidogenic biomass discharge (e.g. by gravity or pressure head) in packed-bed reactors be evaluated to maintain the value of sOLR at a constant level (near 0.97 g-Total carbohydrates g-VS−1 h−1) thus obtaining, a continuous and stable hydrogen production. Not least, periodicals discharge of aging cell may lead to a cellular renewal in the system producing hydrogen hindering the Wood–Ljungdahl pathway.